Random crashing?

As I've continued making videos in Vegas, I get more frequent crashes each time. With my first and second video, I hardly had any crashes. But lately Vegas has crashed every 5 minutes. What could be causing this?

It could be the version of Vegas Pro that you are using, or a conflict with some other software installed on your OS, or the media that you are using, but without knowing anything about any of these things it's really hard for anyone to say what might be causing it. Why don't you tell us more about what software you are using and what you are doing with it before it crashes and see if anyone has an ideas.

I am using Vegas Pro 13. All media is in the same folder, and don't know of any other software that might be messing with it. I'm editing the video like anybody would, dragging events on the timeline, adding new media. But even without editing anything, even so much as PLAYING the preview makes it crash.

That's your problem. Vegas Pro does not work well with Xvid. You need to transcode that video into a format that Vegas can edit. Try converting it to M-JPEG with PCM audio using AviDemux 2.5 (don't use 2.6, only 2.5 work with Vegas Pro)